A positron is a particle that has the same mass as an electron, but with an opposite charge; the polar opposite of an electron. Positrons are formed when a nucleus has too many protons rather than neutrons. In the case where this situation occurs, a proton is converted into a neutron, and a positron is emitted from the nucleus thereafter; the atomic mass remains unchanged, because while the neutron number has gone up by one, the protons number has gone down by one. However, this results in a change in atomic number, meaning a different element is produced eg. Carbon-11 undergoes positron radiation to become Boron-11. The positron then travels its own pathway until it collides with an electron, resulting in either elastic scattering or annihilation.